In article <335f52d8.180382099@news.cinternet.net>, hult@cinternet.net says...
>On 12 Apr 1997 05:50:40 GMT, charlesw99@aol.com (CharlesW99) wrote in
>part in message <19970412055000.BAA25991@ladder01.news.aol.com>:

>>Every test I've read shows that Macro (in this case, Micro) lenses can be
>>used at infinity with excellent results. These lenses are specially
>>corrected at near focus.

>And on Mon, 14 Apr 1997 12:55:40 -0700, duane
>wrote in part in message <33528BBC.655D@dontspamme.org>:
>>i think you're putting too much faith in the rumor surrounding
>>where macro lenses are optimized. sure, some may perform
>>best in close range, however, that doesn't mean that they
>>don't outperform other lenses at other distances as well.

>One lens design variable, is in fact, the focal distance at which the
>lens is to be used, and, in fact, lens are optimized for a specific
>range of distances. But by causing the relative position of
>elements/groups in the lens to change as the focusing distance is
>varied with the lens mount, a lens designer can cause the design to
>adjust (re-optimize, so to speak) as a function of the position of the
>lens's focusing mount. Nikon's jargon for this is Close-Range
>Correction (CRC). Some lens designs are inherently better than others
>over a broader range of focusing distances regardless of whether CRC
>(aka "floating element") is used or not.
[The rest of a really excellent coverage of this subject by Marc Hult
was deleted for space reasons - go back and read it. D.R.]

I just wanted to extend the last point above by pointing out that
some newer macros may still have problems in some parts of their
focus range. Two 60mm Nikkors that I have tried, while truly excellent
macro lenses, did show corner softness near infinity-focus until well
stopped down. I have heard that this is also true of the AF 200mm Nikkor,
but I have not checked this. The 105mm AF Micro-Nikkors, while sharp in
the corners near infinity-focus at wide apertures, often show a bit of
a problem with the image plane not being exactly parallel with the film
plane (probably as a result of a mechanical design that makes focus too
fast near infinity-focus, possibly resulting in a tighter tolerance
requirement than usual for the focus assembly of this lens). The newer
AF macro designs do seem to be generally better for macro use than
the MF designs, though the 55mm f2.8 and 105mm f2.8 MF Micro-Nikkors
were unusually sharp near infinity-focus (hmmmm....;-).
Hope This Helps (or, "DR"....;-)